Light stable composition containing a blend of a synthetic rubber and a salicylate polymer



United States Patent LIGHT STABLE COMPOSITION CONTAINING A BLEND OF ASYNTHETIC RUBBER AND A SALICYLATE POLYMER Carleton T. Handy and Henry S.Rothrock, Wilmington,

Del., assignors to E. I. du Pont de 'Nemours and Company, Wilmington,Del., a corporation of Delaware No Drawing. Application September 28,1956 Serial No. 612,895

20 Claims. (Cl. 260-455) This invention relates to new polymericcompositions. More particularly, it relates to organic polymers for useas supported coatings, self-supporting films, sheets, filaments, shapedobjects, etc., which polymers have been stabilized against degradationby ultraviolet light.

This application is a continuation-in-part of our application Serial No.511,780, filed May 27, 1955, the disclosure of which is herebyincorporated herein.

Many organic polymeric materials are sensitive to light in theultraviolet range and particularly to radiations in the wavelength rangeof about 2300-3600 A. units. This is especially the case with organicpolymers containing chlorine, oxygen or sulfur as constituent atoms inaddition to carbon and hydrogen. When such polymers are exposed toradiations in the above-mentioned range, which are found in sunlight orare emitted by fluorescent lamps, sunlamps, arc lights and the like,they undergo changes which result in a decrease in, or even completeloss of, such important properties as strength, elasticity, pliabilityand electric-insulating capacity. Furthermore, the lightsensitivepolymers may acquire an undesirable color on exposure, which rendersthem unsuitable for many uses.

It has been proposed to prevent or decrease the effects of lightdegradation by incorporating in the polymers susceptible to it smallamounts of monomeric substances containing phenolic and/or carbonylgroups, such as, for example, salicylic acid esters. These compoundsatford substantial protection against ultraviolet light but they havethe inherent disadvantage of impermanence, that is, they are graduallyremoved from the polymer through their volatility, or washed out of itduring laundering or dry-cleaning operations, or they can migrate fromone region to another in shaped objects made of the polymer. I Thisinvention has as an object the stabilization of polymeric materialssubject to deterioration on exposure to ultraviolet light. A furtherobject is the provision of compositions of such polymeric materialsstabilized against such deterioration. Another object is such stabilizedcompositions of increased stability permanence. Still another object issuch stabilized compositions free from migration of stabilizer. A stillfurther object is the prevention or substantial retardation of thedeterioration of polymeric materials by ultraviolet light through theuse of polymeric stabilizers which, because of their nonmigrating andnon-volatile character, remain permanently associated with the polymerto be protected. Other objects will appear hereinafter.

These objects are accomplished by the compositions of this inventionwhich comprise 1) an organic polymer containing carbon and hydrogen, anyother constituent atoms present in the polymer molecule being chlorine,oxygen or sulfur; and (2) another polymer having a molecular weight ofat least 10,000 and containing in the combined form at least 3% byweight of (a) salicylate 'ice units of the formula where n is a cardinalnumber from 0 to l, i.e., vinyl salicylate or allyl salicylate units, or(b) the same salicylate units in the form of their polyvalent metalchelates, said second polymer being present in amount such that there ispresent in the total composition from 0.5 to 25% of its weight ofsalicylate units.

The most important classes of polymers which can be stabilized againstultraviolet light degradation through the present invention are polymersof vinylidene monomers, polyesters and cellulosic polymers and includethe chlorinated vinyl or vinylidene polymers, e.g., the polyvinylhalides, polyvinylidene chloride, polychloro-2-butadiene- 1,3,polydichloro-Z,3-butadiene-1,2, chlorinated polyethylene, chlorinatedrubber, etc.; the sulfochlorinated hydrocarbon polymers; the polymerizedvinyl esters of aliphatic carboxylic acids, e.g., polyvinyl formate,polyvinyl acetate, polyvinyl butyrate, etc.; the polymeric condensationproducts of polycarboxylic acids with polyhydric alcohols, e.g.,polyethylene terephthalate, polyhexamethylene adipate, polyglycerylphthalate, etc.; regenerated cellulose; cellulose esters, e.g.,cellulose acetate, cellulose butyrate; cellulose ethers, e.g., methylcellulose; polymerized vinyl hydrocarbons, e.g., polyethylene,poly-1,3-butadiene, polyisobutylene, polystyrene; polymerized acrylic ormethacrylic acids or esters; and the like.

The salicylate group-containing polymers which serve as stabilizers forthe polymeric compositions of this invention can be the homopolymers ofvinyl salicylate or allyl salicylate. Preferably, however, they arecopolymers of these monomers with another vinyl monomer. For thispurpose, any vinyl monomer copolymerizable with vinyl or allylsalicylate is suitable. However, it is preferred, for reasons ofcompatibility and good film-forming properties, to use copolymers ofvinyl or allyl salicylate with a monoethylenically unsaturated monomerof one of the following classes: acrylic esters of alkanols of 1 to 4carbon atoms, e.g., methyl acrylate, ethyl acrylate, butyl acrylate;vinyl esters of aliphatic monocarboxylic acids of 1 to 4 carbon atoms,e. g., vinyl acetate, vinyl butyrate; and vinylidene hydrocarbons of 2to 4 carbon atoms, e.g., ethylene, isobutylene. The vinyl or allylsalicylate copolymer should contain at least 3%, desirably at least 5%by Weight of salicylate groups in order to impart appreciable stabilityto the light-sensitive polymer without using an excessive amount of thestabilizing polymer. Appreciable prevention of ultraviolet light damageis in general realized when the total composition, that is, the blend ofpolymer to be stabilized and stabilizing polymer, contains 0.5% of itstotal weight of salicylate groups. Preferably the final compositioncontains between 1% and 10% of its total weight of salicylate groups. Itis unnecessary, and undesirable for economic reasons, that there be morethan about 25 of salicylate groups in the final composition. It is alsodesirable that the final composition contain no more than 50%,preferably no more than 25 by weight, of the stabilizing polymer, inorder that the physical properties of the polymer to be protected be notmodified to too large a degree.

The stabilizing polymer, whether it be a homopolymer or a copolymer ofvinyl or allyl salicylate, should have a molecular weight of at least10,000 and preferably above about 25,000 in order to possesssatisfactory resistance to evaporating, migrating or leaching in theshaped polymeric articles in which it is present, and film-formingproperties when it is used as a coating on a light-sensitive polymer.These properties are especially important in polymeric compositions foruse in applications such as wrapping films, electrical insulation orfabrics. In such applications it is necessary that the light protectingagent be a permanent one. There is no theoretical upper limit to themolecular weight of the polymeric light stabilizers.

The polymers and copolymers of vinyl or allyl salicylate can be preparedby known methods of polymerizing vinyl monomers, such as emulsion orsolution polymerization, using known polymerization initiators of thefree radical-producing type such as ammonium persulfate, hydrogenperoxide, organic peroxides, azonitriles, and the like. Under controlledconditions, it is possible to obtain in a reproducible manner copolymersof varying composition, depending upon the relative proportions ofcomonomers in the reaction medium. The polymers and copolymers arenormally obtained as essentially colorless materials ranging in physicalappearance from tough transparent resins to stiff, opaque solids. Aspecific and particularly important class of vinyl and allyl salicylatecopolymers, those in which the comonomer is ethylene, and the polyvalentmetal chelates of these copolymers, are described and claimed in thecopending application of Handy and Rothrock, Serial No. 511,780, filedMay 27, 1955.

The salicylate polymers which serve as stabilizers in the composition ofthis invention can have their salicylate groups partly or wholly presentin the form of chelates with polyvalent metals. These polymers, whichcontain a multiplicity'of chelate-forming structures of the type in thecase of vinyl salicylate, or

CH;CH

in the case of allyl salicylate, are capable of forming with polyvalentmetals chelated products which are crosslinked through the six-memberedchelate rings. To illustrate, with a divalent metal Me and polymerscontaining vinyl salicylate units, the resulting chelated polymer willbe crosslinked through units of the type where the ring arrows representcoordinate linkages.

More complex spatial structures are formed when the chelating metal hasa valence higher than two.

The chelate crosslinked salicylate polymers, when such are desired forthe purposes of this invention, may be conveniently prepared by theprocess of application Ser. No. 535,520, filed by Hoover and Miller onSeptember 20, 1955. This new process, which has been calledtranschelation, consists broadly in treating an organic compound (e.g.,a polymer) containing a plurality of chelateforming structures with achelate of a polyvalent metal with a volatile chelating agent, i.e., achelating agent boiling below 300 C. at 760 mm. pressure, andevaporating the volatile chelating agent, thereby leaving a polymercrosslinked through metal chelate groups. What takes place in thisprocess is a ligand exchange (organic compounds containing chelatingstructures being termed ligands), that is, a transfer of the metal fromthe chelating structure of the volatile chelating agent to those of thenon-volatile polyligand. When the number m of chelate-forming structuresin the non-volatile polyligand and the principal valence n of the metalare each at least two and the sum of m and n is at least five, achelated polymer is formed and crosslinking through chelate rings takesplace between the polymer molecules.

The outstanding advantage of the transchelation process just describedis that the non-volatile polyligand and the polyvalent metal chelate ofa volatile chelating agent can be combined in intimate admixtures, suchas homogeneous solutions, without precipitation of the crosslinked,chelated polymer. Thus, these intimate mixtures can be formed, storedand handled at will, and it is only on removal of the volatile materialsby evaporation that formation of the crosslinked polymer takes place.This is because of equilibrium between volatile and non-volatile ligandsexists in the solutions, which is shifted, with formation of the chelatecrosslinked polymer, when the volatile ligand is removed.

The intimate mixture of the polymer polyligand, i.e., the polymercontaining salicylate groups, and the metal chelate of a volatilechelating agent need not be a homogeneous solution at room temperature.It is only necessary that its components form a homogeneous system atthe temperature at which the ultimate shaped object (film, sheet,filament, etc.) is being formed. Additional inert solvents are notessential but are often used to aid in forming a solution. It is oftendesirable to add to the mixture a small additional amount of a volatilechelating agent, e.g., acetylacetone, as insurance against prematuregelation.

The relative proportions of polymeric polyligand and polyvalent metalchelate of a volatile chelating agent can be such that there is presentthe calculated quantity of metal sufficient to chelate all thesalicylate groups in the polyligand. However, in general, chelatedpolymers containing less than that amount of metal are preferred becauseof their greater flexibility and homogeneity. The desired quantity ofmetal can be introduced either by reacting a polyligand containingrelatively few salicylate groups with the calculated amount of metalchelate, or by reacting a polyligand richer in salicylate groups withless than the calculated amount of metal chelate.

The compositions of this invention can be intimate blends of theultraviolet light-sensitive polymers with the salicylate polymer; orthey can besuch that the salicylate polymer is spread as a uniform layeror coating over the surface of the ultraviolet light-sensitive polymer,the latter being present as a shaped object, e.g., film, sheet,filament, or molded article; or both types of compositions can bepresent in the same object. Blends of the two polymers can be preparedby any suitable method, e.g., intimate mixing of the solid polymers,milling on cold or hot rolls or solution or dispersion mixing.

A recently discovered method of bonding the two polymers consists inexposing to high energy radiation, such as that supplied by a Van deGraaff accelerator, a shaped object of the light-sensitive polymerimmersed in or impregnated with monomeric vinyl or allyl salicylate, ora mixture thereof with another polymerizable monomer. By this procedure,which is illustrated in one of the following examples, the monomerpolymerizes and there is formed a tenacious and permanent bond betweenthe two polymers.

Chelation of the salicylate polymer, if it is desired, can be carriedout during the blending operation or after coating. For example, asolution containing the salicylate polymer and the desired amount ofchelate of the polyvalent metal with a volatile ligand [e.g.,tris(ethylacetoacetato)-aluminum or bis(acetylacetono)nickel] can beintimately mixed with the light-sensitive polymer, as such or insolution. Upon evaporation of the solvents and heating, theabove-described transchelation process takes place, leaving an intimateblend of the light-sensitive polymer with the partly or wholly chelatedsalicylate polymer. Coatings of the salicylate polymer, as such or inthe chelated form, can be deposited on shaped objects of light-sensitivepolymer by conventional means, such as solvent casting or hot pressing.

The following examples are illustrative of the invention.

Example I A methyl acrylate/vinyl salicylate copolymer was prepared asfollows: A solution of g. of vinyl salicylate, 30 g. of methyl acrylateand 0.1 g. of benzoyl peroxide in 100 ml. of thiophene-free benzene washeated to reflux for 30 minutes. The resulting clear, viscous solutionwas stirred for 30 minutes with 10 ml. of absolute ethanol to destroythe excess peroxide. Removal of the solvents and unchanged monomers left29.2 g. of a copolymer containing, as shown by carbon and hydrogenanalysis, 22% by weight of polymerized vinyl salicylate and 78% byweight of polymerized methyl acrylate.

This polymer, with part of its salicylate groups chelated, was used tostabilize a polymer against discoloration by ultraviolet light asfollows: A mixture of 21 g. of a copolymer of vinyl chloride (87% byweight) and vinyl acetate (13% by weight) having an inherent viscosityof 0.53 (available commercially under the name Vinylite VYHH) and 7 g.of the above 78/ 22 methyl acrylate/vinyl salicylate copolymer wasblended by milling on rolls heated to l10-115 C. To the mixture beingmilled was added 0.58 g. of tris(acetylacetono)aluminum with a littleadditional acetylacetone as stabilizer. This amount of monomeric metalchelate is sufiicient to chelate about 50% of the salicylate groups inthe polymer mixture. Milling was continued until a homogeneous blend wasobtained, after which the rolls were heated to 130 C. to complete thetranschelation reaction and permit the acetylacetone to escape. Theresulting sheet was press polished at 150 C. to give a transparent thinsheet of 7.7 mil thickness. This sheet was subjected to an acceleratedexposure to ultraviolet light for 880 hours, together with a similarsheetot unmodified 87/13 vinyl chloride/vinyl acetate copolymer as acontrol.- The apparatus (Weather-O- Meter) was that used in ASTM TestD-822-46-T and described in Part 6 of ASTM Standards, 1952 edition. Atthe end of this test, there was a striking difference in color betweenthe two samples. The control sheet was severely discolored, whereas thesheet of stabilized polymer was only light yellow in color.

Example II The polymeric ultraviolet light stabilizer used in thisexample was a methyl acrylate/ vinyl salicylate copolymer similar tothat used in Example I but containing 18% by Weight of polymerized vinylsalicylate. The polymer to be stabilized was a chlorinated ethylenepolymer also containing sulfonyl chloride groups (see US. Patent2,586,363). It contained about 29% chlorine and about 1.3% sulfur.

Two similar films, 3 mils thick, were cast from benzene solutions. Thefirst one (sample A) consisted of the unmodified sulfochlorinatedpolyethylene. The second one (sample B) was sulfochlorinatedpolyethylene containing 10% of its weight of the methyl acrylate/ vinylsalicylate copolymer and containing in addition,bis(acetylacetono)nickel II in an amount sufiicient to chelate all thesalicylate groups present. The two film samples were heated to 100 C.under reduced pressure to remove the solvent and (in the case of sampleB) to complete the transchelation reaction by removing theacetylacetone. The films were then talced lightly to reduce surfacetack. Their initial color and film properties were noted, and thesamples were then exposed to ultraviolet light as in Example I for 500hours.

At the end of this test, sample A (the control) had become dark and hadundergone very considerable embrittlement. In contrast, sample B was notmaterially changed in color and, furthermore, showed no embrittlementwhatever. The striking difference between sample A and sample B is shownby the following table of properties:

Example III This example illustrates the coating with polymericstabilizers of a polymer sensitive to ultraviolet light, in this casepolyethylene terephthalate. Protective coatings about 0.1-0.2 mil thickof the vinyl salicylate polymers described below as A, B, and C wereapplied by solvent casting to polyethylene terephthalate films 1 mil inthickness.

(A) Homopolymer of vinyl salicylate. This was prepared by heating at 90C. for 48 hours in a pressure vessel a solution of 25 g. of vinylsalicylate and 0.2 ml. of 2,2-bis(tert.-butylperoxy)butane in 40 ml. ofchlorobenzene. The solvent and unreacted monomer were removed bysteaming, leaving 23 g. of a brittle, transparent polymer of vinylsalicylate having an inherent viscosity of 0.35, measured in 0.5%concentration in m-cresol.

(B) A nickel chelate of an ethylene/vinyl acetate/vinyl salicylate72/21/7 terpolymer, prepared as follows: A pressure vessel was chargedwith 15 g. of vinyl salicylate, 35 g. of vinyl acetate, 0.2 ml. oftert.-butyl peroxide, 25 ml. of chlorobenzene and 75 ml. of benzene. Thevessel was sealed, heated to 135 C., pressured with ethylene to 650 atm.and these conditions were maintained for 4.9 hours. The resulting softsponge of copolymer was steamed to remove solvent and unreactedmonomers. There was left 57 g. of a transparent copolymer of inherentviscosity 0.94 in 0.1% solution in tetrahydronaphthalene at 125 C. Ithad a saponification equivalent, measured in pyridine, of 355, andinfrared analysis indicated the presence of 7% of vinyl salicylate. Fromthese data it was calculated that the polymer contained, by weight, 72%ethylene, 21% vinyl acetate and 7% vinyl salicylate. A solution of 5 g.of this polymer in 35 ml. of chloroform was treated with a solution of0.2 g. of tris(butyl acetoacetato)nickel in 2.5 ml. of chloroform. Thisamount of nickel chelate is that calculated to chelate 50% of thesalicylate groups in the polymer. A few drops of acetylacetone wereadded to the solution to prevent premature gelation.

(C) An /15 vinyl acetate/vinyl salicylate copolymer, prepared byrefluxing for 12 hours in a nitrogen atmosphere a solution of 15 g. ofvinyl salicylate, 85 g. of vinyl acetate and 1 g. ofazobis(isobutyronitrile) in 200 ;ml. of tert.-butylv alcohol. Thesolvent and unreacted monomers were removed with steam, leaving 98 gxofthe copolymer as a white resin, inherent viscosity 0.72 in benzene.Analysis (C, 57.38%; H, 6.75%) indicated that the copolymer contained15% by weight of vinyl salicylate.

Coatings were applied from the above solutions onto polyethyleneterephthalate film 1 mil thick as follows:

(A-l) A 30% solution of the polyvinyl salicylate (A) in acetone wasprepared and doctored onto the base polyester film. A one-mil coating ofthe polymer solution was applied, air-dried and then dried 110 C. in theoven. The final coating was less than 0.1 mil in thickness.

(B-l) The polymer-nickel chelate solution described above in (B) wasdoctored onto the base polyester film; The coated film was dried in anoven at 120 C. for 5 minutes, during which time solvents and volatilesevaporated and transchelation took place, leaving a film of chelatecrosslinked polymer on the base polyester film.

(C-l) The copolymer described in (C) above was applied onto the basepolyester film by the procedure described under A-l.

All these coatings showed good adherence to the polyethyleneterephthalate base.

The coated polyethylene terephthalate films were sub jected with anuncoated control to accelerated weathering tests at 5560 C. Theapparatus used was essentially that described in method 6021 of FederalSpecification L-P-406 except that the light was provided by specialfluorescent sunlamps giving major radiation in the range of 2800-3200 A.units; the lamps and the samples were mounted vertically; and constanthigh humidity (RH. =34%) was used instead of a fog spray. The light fromthis type of test lamp degrades polyester film much more rapidly thaneither sunlight or the light from a carbon arc lamp.

After 95 hours of exposure, the degree of embrittlement of each film wasdetermined by measuring the residual average elongation at break, whichwas initially about 62% for all films. Polymer degradation in each filmwas also estimated by determining the inherent viscosity of the polymerafter 95 hours exposure, the initial inherent viscosity being about 0.55in each case. The results are shown in the table below.

Coating Percent Inherent Coating Thickness, Elongation Viscosity MilsA-L 0.1 31 0.46 3-1. 0.1 40 0.42 o-1- 0.1 0. 32 Control 0 0 0.30

The above table shows that the coatings had provided stabilization invarying degree, in spite of their thinness.

Example IV salicylate Control, g.

Blond, g.

Original tear strength 133 102 Tear strength after 100 hours exposure 93too brittle to measure.

8 Example V 0 posure to sunlight and weather in Florida, whereas anuncoated control was severely grayed and eroded.

Example VI A copolymer of methyl acrylate and allyl salicylate wasprepared by heating the monomers in 60:40 weight ratio, in benzenesolution at 70-75 C. for 2 hours in the presence ofazobis(isobutyronitrile) as the initiator. The copolymer was isolated bypouring the solution into methanol. It contained, by weight 87% ofmethyl acrylate and 13% of allyl salicylate.

A uniform coating of this copolymer was deposited from solution onto apolyethylene terephthalate film 1 mil thick. The coated sample and anuncoated control were then subjected to an accelerated weathering testas described in Example III. After hours exposure, the control was veryseverely embrittled, as shown by a decrease in elongation at break from75% to 3%, and it had lost one-third of its initial tenacity. Incontrast, the coated film (tested after stripping off the coating) stillshowed 68% elongation at break and a loss in tenacity of only 13%.

Example VII A coating solution was prepared by dissolving in xylene an88/12 (by weight) copolymer of ethylene and vinyl salicylate, sufiicienttris(acetylacetono)aluminum to chelate 75% of the chelating structurespresent in the copolymer, and a little acetylacetone to stabilizeagainst gelation. This solution was applied to a commercial regeneratedcellulose film 13 mils thick in amount sufiicient to deposit on the film7.45 g. per square meter of the chelate cross-linked polymer afterevaporation of the solvents and heating.

This coated film and an uncoated control were sub jected to acceleratedexposure tests in the apparatus of Example II. After 1020 hoursexposure, the coated sample had retained its original dimensions,tensile strength and modulus and had suffered only a moderate loss inelongation. In comparison, the uncoated control after only 200 hours hadundergone severe shrinkage and substantial losses in tensile strength,modulus and elongation. After 1020 hours, the control had disintegratedcompletely.

Example VIII A sample of polyethylene terephthalate film approximately0.8 mil in thickness was placed in a glass cell with thin sides. Thecell was filled with monomeric vinyl salicylate, sealed and wrapped inaluminum foil. It was then given 10 passes in a Van de Graaffaccelerator, one pass consisting of exposing the sample, traveling at aspeed of 2 cm./sec., to an electron beam having an electron energy of 2m.e.v., using a scan width of 20 cm., a sample-to-window distance of 10cm., and a beam current of 250 microamperes. After irradiation, the cellwas opened and the film was continuously extracted with methyl ethylketone for 16 hours and dried at 60 C. It had gained 3.6% in weight andits thickness had increased to approximately 0.95 mil. The presence ofpolyvinyl salicylate was confirmed by the fact that the film absorbedradiation in the region of 3l00-3400 A. whereas a control film showedlittle absorption in this region.

The composite prepared as described above had an inherent viscosity of0.55. After 75 hours exposure in the accelerated weathering apparatus ofExample III, the inherent viscosity of the composite was still 0.50,showing that little degradation had taken place. As a control, a sampleof polyethylene terephthalate film was irradiated in the same manner (10passes) without the vinyl salicylate. Its inherent viscosity was 0.54.After 9. 75 hours exposure in the same weathering apparatus, itsintrinsic viscosity had decreased to 0.40.

This invention has been illustrated with reference to certain specificpolymeric compositions, but it includes broadly compositions comprisingany polymer susceptible to degradation by light of wavelength in therange of about 2300-3600 A. units and, in amount sufiicient forappreciable stabilization, a polymer containing vinyl salicylate orallyl salicylate units, as such or as metal chelates. Thus, in additionto the compositions shown in the foregoing examples, there can beprepared compositions of ethylene/vinyl acetate copolymers withethylene/vinyl salicylate copolymers; of polyvinyl chloride with allylsalicylate homopolymer, vinyl acetate/allyl salicylate copolymer orvinyl formate/ vinyl salicylate copolymer; of polyvinylidene chloridewith ethylene/allyl salicylate copolymer or vinyl butyrate/vinylsalicylate copolymer; of poly-chloro-2-butadiene-1,3 with methylacrylate/allyl salicylate copolymer, isobutylene/vinyl salicylatecopolymerof butyl acrylate/vinyl salicylate copolymer; of chlorinatedpolyethylene with vinyl salicylate homopolymers; of polyvinyl formatewith vinyl acetate/ allyl salicylate copolymer; of polyhexamethyleneadipate with methyl acrylate/ vinyl salicylate copolymer; ofpolyglyceryl phthalate with polyvinyl salicylate; of cellulose acetatewith butyl acrylate/vinyl salicylate copolymer; of cellulose or methylcellulose with methyl acrylate/ vinyl salicylate copolymer; and thelike. In preparing polymer blends it is desirable, although notessential,

that the salicylate group-containing polymer be compatible with thelight-sensitive polymer. This is of no importance when thelight-sensitive polymer is coated with the polymeric stabilizer.

In the compositions of this invention, part or all of the vinylsalicylate or allyl salicylate units may be present as chelates ofpolyvalent metals. The polyvalent metals known to form chelatesreadilyare listed in the book by Martell and Calvin entitled Chemistry of theMetal. Chelate Compounds (Prentice-Hall, Inc., New York, 1952),particularly at page 182. Preferred examples of metals suitable forchelation with the salicylate polymers are aluminum and zirconium,because their chelates 'are colorless and have particularly goodresistance to hydrolysis. Other suitable metals are zinc, magnesium, andberyllium, whose chelates are also colorless; and copper, manganese,iron, cobalt and nickel when colored products are desired or notobjectionable. Nickel and copper chelates are particularly effective asultraviolet light screens.

For the purposeof preparing the chelate cross-linked polymers bytranschelation, that is, reaction of the poly- .meric polyligand with apolyvalent metal chelate of a volatile chelating agent, any suitablechelating agent boiling below about 300 C. at 760 mm. will serve. Thepreferred ones are those most available and most economical, which arein general the 1,3-diketones, the

fi ketoesters and the aromatic oc-hYdIOXY aldehydes and esters.Specifically preferred chelating agents are acetylacetone,3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, propionylacetone,trifluoroacetylacetone, 2-furoylacetone, Z-thenoylacetone, ethylacetoacetate, butyl acetoacetate, salicylaldehyde, methyl salicylate,and the like. Thus, there may be employed for reaction with the polymersor copolymers of vinyl salicylate or allyl salicylate the followingrepresentative polyvalent metal chelates of volatile chelating agents inaddition to those illustrated in the examples: bis(ethylacetoacetato)zinc; bis(ethyl acetoacetato)mbalt II; bis(butylacetoacetato) copper II; bis(salicylaldehydo)copper II;bis(acetylacetono)magnesium; tetrakis(ethyl acetoacetato)zirconium;tris(methyl salicylato)aluminum; bis(methyl salicylato) beryllium;bis(ethyl acetoacetato)magnesium; diisopropyl bis(ethylacetoacetato)titanate IV; bis(acetylacetono) manganese II; tris(ethylacetoacetato)iron III; tris(acetylacetono)iron III;bis(1,1,1-trifluoro-3-benzoylacetono) copper II;trisEZ-(furoyl)acetono1aluminum; and the like.

When a chelated polymer is desired as the light stabilizer, thepolymeric polyligand is desirably treated with sufiicient metal chelateto produce a final polymer containing at least 0.001 gram atom, andpreferably from, 0.005 to 0.03 gram atom of metal per g. of chelatedpolymer. In this treatment and in the subsequent evaporation of thevolatile chelating agent, no additional solvent is required in manycases, although an additional solvent is often desirable to provide asolution of convenient viscosity for the purpose of producing shapedarticles. The solvent can be any volatile liquid'which is substantiallyinert towards the two components of the mixture of solution. Suitableorganic solvents include aromatic hydrocarbons, e.g., benzene, tolueneor the xylenes; acyclic or cyclic ethers, e.g., di-n-butyl ether,tetrahydrofuran; ketones, e.g., methyl isobutyl ketone, cyclohexanone;halohydrocarbons, e.g., chloroform; and the like. The quantity ofsolvent is not critical and needs only be sufiicient to decrease theviscosity of the composition to a level practical for film casting orsimilar uses. If some tendency to precipitation or gelation is noted onmixing the reactants, such tendency can be overcome by adding a slightexcess of the volatile chelating agent, or of a different one havinggreater chelating strength than the polymeric ligand to keep thechelated polymer in solution.

The chelated polymers cast or otherwise formed from these compositionsbecome tack-free rapidly upon airdrying, and even more rapidly uponbaking, for example, at temperatures of S0 to 200 C. for from 15 minutesto two hours. The resulting products are polymers of vinyl or allylsalicylate crosslinked through the sixmembered chelate rings formed bythe polyvalent metal and the salicylate groups.

The polymeric products of this invention are useful in all applicationswhere the unstabilized light-sensitive polymers are useful. They are, ofcourse, of special utility wherever shaped objects made of thesepolymers (e.g., filaments, films, sheets, coatings, moldings) areexposed to light rich in radiations in the ultraviolet range.Specifically, the polymeric compositions of this invention are useful asprotective coatings for surfaces such as wood, fabrics and especiallymetals, e.g., refrigerators, autobodies, furniture, and the like; asflexible sheets for use in articles such as bags, hat covers, overshoes,capes, and the like; as filaments for fabrics for outer wear; aswrapping materials for food products; as book covers, flexible wirecoating, electrical insulation, electrical tape; as glass laminates,sunshades, umbrellas, visors; in the manufacture by molding or extrudingof shaped objects such as tumblers, chips, tubes, novelty articles; andthe like.

In comparison with prior blends of light-sensitive polymers withmonomeric salicylic acid esters, the polymeric composites of thisinvention have the advantage that the stabilizer is substantiallypermanent and non-removable by physical procedures such as solventextraction.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed for obvious modifications will occur to those skilled in theart.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A composite resistant to light radiations in the wave length range ofabout 2300 to 3600 A., containing an organic polymer subject todeterioration on exposure to light and containing carbon and hydrogenwith any additional elements selected from the class consisting ofchlorine, oxygen and sulfur, said polymer being selected from the groupconsisting of polymers of vinylidene monomers, polyesters and cellulosicpolymers and as a stabilizer therefor not more than 50% by weight of asecond polymer of molecular weight of at least 10,000 selected from thegroup consisting of homopolymers of vinyl and allyl salicylate andcopolymers of these monomers with monoethylenically unsaturatedmonomers, said second polymer being present in amounts such that from0.5 to 25% by weight of the composite is salicylateunits.

- 2. The composite of claim 1 wherein the second polymer contains inaddition to the salicylate monomer, units of a vinyl monomer differentfrom that furnishing the salicylate units. 1

3. The composite of claim 1 wherein the second polymer contains units ofan acrylic ester of an alkanol of 14 carbons, in addition to thesalicylate units.

4. The composite of claim 1 wherein the second polymer contains units ofa vinyl carboxylate, in addition to the salicylate units.

5. The composite of claim 1 wherein the second polymer contains units ofa vinylidene hydrocarbon of. up to 4 carbons, in addition to thesalicylate units.

6. The composite of claim 1 wherein the salicylate units are present inthe form of a homopolymer of the salicylate monomer.

7. The composite of claim 1 wherein the polymer containing salicylateunits is in lamellar relationship to the organic polymer subject todeterioration on exposure to light. 1

8. The composite of claim 1 wherein the polymer containing salicylateunits is in intimate admixture with the organic polymer subject todeterioration on exposure to light.

9. The composite of claim 1 wherein the salicylate units are present inthe form of chelates thereof with a polyvalent chelating metal.

10. A composite according to claim 5 wherein the light-sensitive polymeris polyethylene and the second polymer an ethylene/vinyl salicylatecopolymer.

11. A composite according to claim 5 wherein the lightsensitive polymeris polyethylene terephthalate and the second polymer is anethylene/vinyl salicylate copolymer.

12. The composite of claim 9 wherein the second poly- 1'2 mer containsin addition to the salicylate monomer, units of a vinyl monomerdifferent from that furnishing the salicylate units.

13. The composite of claim 9 wherein the second polymer contains unitsof a vinylidene hydrocarbon of up to 4 carbons, in addition to thesalicylate units.

14. The composite of claim 9 wherein the salicylate units present in theform of a homopolymer of the salicylate monomer.

15. The composite of claim 9v wherein the polymer containing salicylateunits is in lamellar relationship to the organic polymer subject todeterioration on exposure to light.

16. The composite of claim 9 wherein the polymer containing salicylateunits is in intimate admixture with the organic polymer subject todeterioration on exposure to light.

17. A film formed of the composition of claim 1.

18. A filament formed of the composition of claim 1.

19. A coated object comprising a substrate having a coating of thecomposition of claim 1.

20. A composite resistant to light radiations in the wave length rangeof about2300 to 3600 A. containing an organic polymer subject todeterioration on exposure to light and containing carbon and hydrogenwith any additional elements selected from the class consisting ofchlorine, oxygen and sulfur, said polymer being selected from the groupconsisting of polymers of vinylidene monomers, polyesters and cellulosicpolymers and as a stabilizer therefor not more than by weight of asecond polymer of molecular weight of at least 10,000 selected from thegroup consisting of homopolymers of vinyl and allyl salicylates andcopolymers of these monomers with monoethylenically unsaturatedmonomers, and polyvalent metal chelates of such polymers wherein thepolymer is cross-linked through six-membered chelate rings formed by thepolyvalent metals and the salicylate ester groups, said second polymerbeing present in amount such that from 0.5 to 25% by weight of thecomposite is salicylate units.

No references cited.

1. A COMPOSITE RESISTANT TO LIGHT RADIATIONS IN THE WAVE LENGTH RANGE OFABOUT 2300 TO 3600 A., CONTAINING AN ORGANIC POLYMER SUBJECT TODETERIORATION ON EXPOSURE TO LIGHT AND CONTAINING CARBON AND HYDROGENWITH ANY ADDITIONAL ELEMENTS SELECTED FROM THE CLASS CONSISTING OFCHLORINE, OXYGEN AND SULFUR, SAID POLYMER BEING SELECTED FROM THE GROUPCONSISTING OF POLYMERS OF VINYLIDENE MONOMERS, POLYESTERS AND CELLULOSICPOLYMERS AND AS A STABILIZER THEREFOR NOT MORE THAN 50% BY WEIGHT OF ASECOND POLYMER OF MOLECULAR WEIGHT OF AT LEAST 10,000 SELECTED FROM THEGROUP CONSISTING OF HOMOPOLYMERS OF VINYL AND ALLYL SALICYLATE ANDCOPOLYMERS OF THESE MONOMERS WITH MONOETHYLENICALLY UNSATURATEDMONOMERS, SAID SECOND POLYMER BEING PRESENT IN AMOUNTS SUCH THAT FROM0.5 TO 25% BY WEIGHT OF THE COMPOSITE IS SALICYLATE UNITS.